I will try this before or after the AppGameKit game jam (depending on time) as I will be releasing a Mac and Windows version of the app on itch.io. The only problem with this solution is that it requires the developer to have an Apple Developer license, which is quite a lot of money a year just to change an icon. I do have the developer license as I had an app on the iOS App Store earlier in the year, but if I'm not planning on releasing apps anytime soon on the iOS or Mac App Stores, it's kind of a pointless expense. I want to change icons in apps I might share on itch.io, so the apps don't need to be signed.